Lumber and method of making the same



April 20, 1937. c, RQZEMA 2,077,714

LUMBER AND METHOD OF MAKING THE SAME Filed Aug. 28, 1933 Patented Apr.20, 1937 UNITED STATES LUMBER AND METHOD OF MAKING THE SAME Charles E.Rozema, Grand Rapids, Mich, as-

signor, by mesne assignments, to Haskelite Manufacturing Corporation,

New York a corporation of Application August 28,- 1933, Serial No.687,122

8 Claims.

All of the pinaceous or coniferous woods have a tendency to check' whenexposed to weather. This tendency is very strong in the case of some ofthese woods, such as fir, cypress, larch, pine,

etc., to which group I shall herein apply the name, fir. Fir plywood isa cheap product but its use is limited by its inherent tendency tocheck. This checking occurs not only in exterior use but also in thecase of panels used in interiors. The application of paint somewhatinhibits but does not prevent such checking.

The object of the present invention is to make it possible in a simplemanner and at a low cost to prevent visible checking of fir or otherwood.

I have discovered that if a piece of fir be faced with strong paper,such as kraft, which will absorb varnish, or other pliablevarnish-absorbing cellulosic material, and the facing be thenimpregnated or partially impregnated with a suitable varnish which isalso allowed to extend above the surface of the paper as a continuousfilm of such varnish, no visible checking develops. Under someconditions the wood may check, but the stresses developed thereby areabsorbed by the cellulosic facing layer, so that the varnish filmremains intact. Furthermore, the protection afforded to the wood isabout the same as though it had thereon several coats of good paint.Therefore, when panels of this kind are used for structural purposesthey require no further painting except for color.

The various features of novelty whereby my invention is characterizedwill hereinafter be pointed out with particularity in the claims; but,

for a full understanding of my invention and of its objects andadvantages, reference may be had to the following detailed descriptiontaken in connection with the accompanying drawing, wherein:

Figure 1 is a view showing the elements to constitutes. plywood paneland two facing layers therefor spaced apart from each other and providedwiththe proper glue coatings, layers or films to produce a three-plycore of wood faced 45 on both sides with paper or other cellulosicmaterial when these elements are glued up in a press; Fig. 2 is an edgeview of the panel at the end of the gluing operation; and Fig. 3 is asection, on a greatly enlarged scale, showing a 50 small fragment of thepanel after it has. been glued, receiving an application of varnish uponone of its faces.

The present invention will be used most widely in connection withplywood panels and, therefore,

56 the detailed description will be confined to this particularembodiment, although it will, of course, be understood that theinvention is not limited to panels or to plywood.

In Fig. 1 of the drawing I have shown three pieces of wood veneer, I, 2,and 3, adapted to be glued together into a three-ply panel. Layers,films or coatings of glue must be placed between the members I and 2 andbetween the members 2 and 3. The character of the glue in theselocations and the manner of applying it may be varied according to thenature of the product desired. In the arrangement shown, the member 2,which may be regarded as the core of the multiple-ply panel, is shown ashaving been coated on both faces with glue, as indicated at 4 and 5. Ifthe members I, 2, and 3 are now glued together in a press or otherwisethe result will be simply an ordinary three-ply panel which may beregarded as illustrative of multiple-ply panels in general.

In accordance with the present invention another ply is added to form afacinglayer. Even though it be not required to guard against checking ofboth faces of the panel, and since one of the faces could therefore beleft in the same condition as heretofore, it is preferable that facinglayers be applied to both sides of the panel. Therefore, in assemblingthe veneers I place underneath the same a facing sheet 6 and lay asimilar facing sheet on top of the veneers. The facing sheets must beglued to the wood and this can conveniently be accomplished by coatingthe upper face of the member I with glue, as indicated at I, and placinga similar glue coating 8 on the under face of the veneer 3. 'When thefive individual pieces appearing in Fig. 1 are pressed together to forma multiple-ply panel, the panel, illustrated in Fig. 2, may be said toconsist of five plies instead of three; two of the plies being thefacing layers or sheets.

After the panel has been glued it is necessary to treat one or both ofthe facing layers before the panel is ready for use. This treatmentconsists in providing coatings in the form of continuous hard protectivefilms so effectively combined with the facing layers that the filmscannot peel off without destroying the paper or other material of whichthe facing layers are composed. In order properly to unite theprotective film with a facing layer on the panel it is necessary thatthe facing layer be composed of materials of a kind into which theprotective material will readily penetrate while the panel is hot. Then,when a protective material of the proper type is applied to the hotpanel, portions thereof form a film upon the surface of the facing layerand other portions penetrate deeply into the same. Preferably theprotective material should permeate the entire facing layer although, ifthe weaker structure resulting therefrom is not objectionable, theprotective material may be allowed to extend only a short distance intothe facing layer.

The protective material or materials may be any resinous substance orsubstances that will exclude moisture, as that is the chief functionthereof; the most suitable being synthetic resin varnishes. By varnishesI mean to include, also, lacquers, enamels and paints. Furthermore,although varnishes, lacquers, enamels, etc., ordinarily contain solventsand non-solvents, this is not essential; but dry resinous materials ofthe proper character and in a fusible condition can successfully beapplied to the hot panel. It should therefore be understood that when Irefer to a varnish I means any or all of these resinous materials orsubstances containing them, whether in dry or other form. The resinouscomponent of the varnish is preferably of the heat-hardening type.

The facing layers should not be unduly thick, nor should they be toothin. Good results are obtained with strong absorbent paper having athickness of from three one-thousandths to seven one-thousandths of aninch.

While the glues employed to unite the wood veneers together may be ofany usual or suitable kinds, I prefer that the glue lines between thepaper and the Wood have a high synthetic resin content and that all ofthe glues be such as to permit the composite panel to be glued upthrough heat and pressure. It therefore follows that when a panel isremoved from the press it is still hot and the absorbent facing layersare in the proper condition readily to absorb varnish deposited upon thesame. I prefer to use an aqueous suspension of highly comminutedparticles of thermosetting varnish-resin which may be sprayed, brushedor otherwise spread over the exposed surfaces of the facing layers andwhich dries sufliciently hard for handling while the panel is cooling.

When varnish must be applied to both sides of the panel, this canconveniently be done by running the hot panel through rollers adapted toconvey to the surfaces of the hot panel an adequate amount of varnish.However, whether the varnish-resin, with or without solvents ornonsolvents, be applied by rollers, by brushing, by spraying, orotherwise, the application of the varnish may be made to one face onlywhere it is not necessary to protect both faces.

The great utility of the present invention will be apparent from thefact that uncoated fir when exposed to weather becomes obviously checkedin as short a time as twelve hours, and the further fact that firprovided with three coats of high grade paint shows checks within a veryfew days under exposure to weather; whereas panels prepared according tomy invention have failed to develop cracks or checking through thefinished surfaces after exposure to weather for three months. In caseswhere the paperis saturated and impregnated with resinous materials andis then glued to the fir, the results are not satisfactory because thepaper seems to be unable to absorb the stresses set up by the checkingof the underlying wood. The reason why this latter method is notsatisfactory can readily be understood. When a sheet of paper isthoroughly saturated with a resinous material and is compressed betweenthe plates of a press, the resulting product is a sheet that is hard andbrittle and does not possess the character of paper that it did beforeentering the press; but the sheet is now essentially a film of resinthrough which cellulosic fibers are distributed. The cellulosic fibersare more or less disintegrated during the pressing operation and thusserve simply as a filler. When stresses are set up in a face veneer of afir panel to which this impregnated and compressed sheet has beenapplied, these stresses cannot be distributed throughout any portion ofthe compressed facing material. The result is that the checks will breakthrough the surfacing layer or, as an alternative, the glue line will besheared at the junction between the veneer and the surfacing layer. In apanel prepared in accordance with my invention, however, the paper orother cellulosic material retains its original character and acts as acushion which yields and absorbs the stresses set up in the underlyingface veneer.

In Figure 3 of the drawing I have shown the paper in the condition inwhich it leaves the press as well as in the completed condition. Thepaper retains its character as a coherent sheet as represented by theright-hand half of the member 6 in Fig. 3; this sheet being simplyunited to the adjacent face veneer I by a glue line Ill. Thevarnish-resin material is shown as being supplied in the form of a sprayC, in sufilcient quantity to cause the paper to be permeated down to theglue line ID, as indicated at H, and leave a thin continuous superficialprotective film I! upon the paper. Since the varnish-resin extends downto the glue line, the paper is strengthened in the vicinity of the glueline while retaining the elastic properties characteristic of the paperfiber.

While I have illustrated and described with particularity the best formof my invention and the best mode of carrying it out, I do not desire tobe limited to the details thus illustrated and described; but intend tocover all methods and materials coming within the definitions of myinvention constituting the appended claims.

I claim:

1. The method of producing a product that will not check of wood havinga tendency to do so, which comprises gluing to a face of the wood by thehot process pliable cellulosic material that will absorb varnish whensuch material is hot, and while the said material is still in a heatedcondition, applying varnish to said material to cause portions thereofto penetrate into said material and the remainder to form a continuousfilm overlying the cellulosic material.

2. The method of producing a product that will not check of wood havinga tendency to do so, which comprises gluing to a face of the woodpliable cellulosic material that will absorb varnish, and applyingvarnish compatible with the glue to said material while the latter is ina heated condition.

3. The method of producing a material that will not check of wood havinga tendency to do so, which comprises gluing to a face of the wood paperthat will absorb varnish and applying suflicie nt varnish compatiblewith the glue to the paper whilethe paper is in a heated condition tocause portions to penetrate into the paper in the vicinity of the glueline and the remainder to form a continuous film overlying the paper.

4. The method of producing a product that will not check of wood havinga tendency to do that will not check of wood that has a tendency to so,which comprises gluing to a face of the wood by means of glue having ahigh resin content paper that will absorb varnish and, 'while the paperis in a heated condition, applying varnish 5 resin to the paper.

5. The method of producing a plywood panel that will not check of woodhaving a tendency to do so, which comprises gluing up by a hot process aplywood panel and facing layers therefor com- 10 posed of pliablecellulosic material and, while the panel is still hot, applyingvarnish-resin to one or both of the facing layers.

6. The method of producing a plywood panel that will not check of woodhaving a tendency 5 to do so, which comprises gluing up by a hot processa wood panel and a facing layer therefor composed of cellulosic materialbetween which and the wood there is a glue line having a high resincontent and, while the panel is still hot, applying 20 varnish-resin tothe facing layer.

7 The method of producing a plywood panel do so, which comprises gluingup by a hot process a wood panel and facing layers of strong paper thatwill absorb varnish and between which facing layers and the body of thepanel are glue lines having a high resin content and, while the panel isstill hot, applying vamish-resin to one or both facing layers. I

8. The method of producing a plywood panel that will not check of woodthathas a tendency to do so, which comprises gluing up by a hot processa wood panel and facing layers of strong paper that will absorb varnishand between which facing layers and the body of the panel are glue lineshaving a high resin content and, while the panel is still hot, applyingto the facing layers an aqueous suspension of varnish-resin in highlycomminuted form.

- CHARLES E. ROZEMA.

